Atlas of Oral Histology by Akramjuaim

5/24/2018 Atlas of Oral Histology by Akramjuaim

1/151

ATLAS

OF

ORAL HISTOLOGY

Prepared by :

D. Akram Nasser Juaim


2/151

Table of content

- Chapter 1 : teeth development.

- Chapter 2 : enamel.

- chapter 3 : dentin.

- chapter4 : pulp.

- chapter5 : cementum .

- chapter6 : periodontal ligaments .

- chapter7 : teeth eruption .- chapter8 : oral cavity .

- chapter9 : salivary glands .

- chapter10 : temperomandibular ligaments .


3/151

Chapter 1 TEETH

DEVELOPMENT


4/151

Chapter 1, Slide 1

Dental laminaDuring the fifth week of

embryonic development,

the oral epithelium

thickens along the futuredental arches to form

the dental lamina.

A, dental lamina;

B, Mesenchymal neuralcrest


5/151

Chapter 1, Slide 2

Bud stageAround the eighth week of

embryonic development, the

mesenchymal neural crest

induces the development of

tooth

buds at ten locations in

the upper and lower dental

lamina. During the bud stage

the dental lamina grows into

the mesenchyme in the shapeof a bud.


6/151

Chapter 1, Slide 3

Cap stage

During the ninth week of embryonic development, the tooth bud

differentiates into a cap-shaped enamel organ extending from the

dental lamina. vestibular lamina develops to separate the gum from

the lip/cheek. During the cap stage, an unequal growth of epithelialcells grows down to form a concavity around the mesenchyme

forming the dental papilla. Other mesenchymal cells encircle

the enamel organ forming the dental sac.

A, Enamel organ; B, Dental lamina;

C, Vestibular lamina; D, Dental Papilla; E, Dental sac


7/151

Cytodifferentiation becomes apparent during the bell stage, when

the epithelial cells outlining the enamel organ can be distinguished

as the inner enamel epithelium and outer enamel epithelium.

The interior of the enamel organ comprises the stellate reticulum,cushiony layer which will protect the developing tooth.

The successional lamina, which will give rise to the secondary

Tooth, arises from the dental lamina.

A, Inner enamel epithelium; B, Outer enamel epithelium;

C,Stellate reticulum; D, Successional lamina;E, Dental lamina; F, Dental papilla; G, Dental sac.

Chapter 1, Slide 4Bell stage


8/151

Chapter 1, Slide 5Cervical loopThe inner enamel epithelium andouter enamel epithelium joint at the

cervical loop, that portion of the

enamel organ which is growing down

into the mesenchyme.

The cells of the inner enamel

epithelium will eventually becomeameloblasts. The layer adjacent to

the inner enamel epithelium is the

stratum intermedium , and will

become important in transporting

nutrients to the future ameloblasts.A, Cervical loop;

B, Inner enamel epithelium;

C, Outer enamel epithelium;

D, Stratum intermedium;

E, Stellate reticulum


9/151

Chapter 1, Slide 6

Cytodifferentiation of inner enamel

epitheliumThe cells of the inner enamel

epithelium (which will become

ameloblasts) are least

differentiated near the cervicalloop and most differentiated near

the incisal cusp of the tooth.A, Cervical loop;

B, Least differentiated;C, Most differentiated


10/151

Preameloblasts initiate the differentiation of odontoblasts

which arise from cells in the dental papilla. The odontoblasts

are called preodontoblasts before they begin the production of

dentin.A, Preameloblasts;

B, Preodontoblasts;

C, Stellate reticullum;

D, Dental papilla

Chapter 1, Slide 7Odontoblastic

differentiation


11/151

Mature, elongated odontoblasts begin the deposition of predentin.

This deprives the preameloblasts of their nutritional source

inducing their differentiation into ameloblasts which then begin to deposit

enamel. Predentin is completely organic when it is formed and gradually ismineralized to form dentin. Enamel is partially mineralized when it is

deposited. Arrows show the direction of movement of ameloblasts and

odontoblasts.A, Odontoblasts; B, Predentin; C, Ameloblasts;

D, Enamel; E, Dentin

Chapter 1, Slide 8Deposition of dentin and

enamel


12/151

Following the formation of the crown , the enamel organ collapses

to form the reduced enamel epithelium which covers the tooth

through eruption. The reduced enamel epithelium consists of the

mature/protective ameloblasts and remnants of the outer layers ofthe enamel organ. Numerous capillaries, which had formed to

supply oxygen and nutrients to the ameloblasts following dentin

formation, surround the reduced enamel epithelium.

A, Reduced enamel epithelium;

B, Maturative/protective ameloblasts; C, Capillary

Chapter 1, Slide 9Reduced enamel epithelium


13/151

Chapter 1, Slide 10

Immature enamelAmeloblasts secrete

immature enamel which is

only partially mineralizedA, Ameloblasts;

B, Immature enamel


14/151

Chapter 1, Slide 15

CalcificationEnamel and dentin is fairly

evenly calcified in the erupted

deciduous tooth (1) but a

gradient of calcification can beseen in the developing

permanent tooth (2) with the

more calcified areas located

in the incisal areas (arrow)A, Enamel;

B, Dentin


15/151

Chapter 1, Slide 18Root formationAfter complete formation of thecrown of the tooth, the root is formed. An

extension of the enamel organ, called the

epithelial root sheath of

Hertwigs,continues to grow apically.The

epithelial root sheath induces the

differentiation of odontoblasts which formroot dentin. The apical most portion of the

root sheath turns inward toward the

radicular pulp Cavity (that portion of the

pulp cavity inside the root) and is called

The epithelial diaphragm.

A, Epithelial diaphragm;

B, Radicular pulp cavity;

C, Dentin; D, Enamel space;

E, Alveolar Bone; F, Root


16/151

Chapter 1, Slide 19Epithelial root sheathTheepithelial root sheath ismade up of inner and outer

enamel epithelial layers without

the other two interposing layers.

Following the induction of

odontoblast and dentin

Formation,the epitheal rootSheath disintegrates forming

epithelialrests, small groups

of epithelial cells that can

remain around the root.A, Radicular pulp cavity;

B, Dentin; C, Dental sac;

D, Point at which

epithelial root sheath

begins to disintegrate;

E, Epithelial diaphragm


17/151

Chapter 1, Slide 20

Cementum formationAs the epithelial root sheath

breaks down, cells from the

dental sac migrate to the

surface of the root dentin and

differentiate into

cementoblasts. These

cells lay down

cementum on the

surface of the root.

A, Cementoblasts;

B, Odontoblasts;

C, Predentin


18/151

Chapter 1, Slide 21Epithelial rests

Remnants of the disintegratedroot sheath called epithelial rests can

remain for long periods of time

following eruption of the tooth.

The first dentin that is formed

is called mantle dentin, while the

remaining dentin is calledcircumpulpal dentin. There is

also a small layer interposed

between these two dentin

Layers of less mineralized

dentin called globular dentin.

A, Epithelial rests;

B, Mantle dentin;

C, Globular dentin;

D, Circumpulpal dentin


19/151

Chapter 1, Slide 22First maxillary deciduous molar

This molar is from a 22-week fetus. The red coloration indicates

the formation of the hard tissues. Enamel and dentin are first formed atthe cuspal region and their formation proceeds toward the cervix of the

toothA, Cusp of molar


20/151

Chapter 1, Slide 23Second maxillary deciduous molar

This molar is from a 19-week fetus. The first deposited

dentin on the mesiobuccal cusp is shown.

A, Dentin on the mesiobuccal cusp


21/151

Chapter 2ENAMEL


22/151

Chapter 2, Slide 1Stria of Retzius

During development of enamel,variations in the metabolism of

the organism cause variations in the

amount of organic material deposited in

the enamel. This causes changes in the

coloration of the enamel that is layed

down at that time so that alternatingdark (higher organic material) and light

(less organic material) banding occurs.

These bands are called Striae of

Retzius. The striae of Retzius

usually intercept the

dentino-enamel junction.A, Stria of Retzius ;

B, Dentino-enamel junction


23/151

Chapter 2, Slide 2Enamel - transverse

ground sectionIn a transverse section of tooth,

the stria of Retzius appear as concentric

bands parallel to the dentino-enamel

junction (DEJ). In addition to the "hypo-

mineralized" dark stria of Retzius, there

also exist hypo-mineralized areas

perpendicular to the DEJ. These are

enamel lamellae (that traverse the entire

thickness of enamel) and enamel tufts

(that traverse the inner third of enamel

adjacent to the DEJ.

A, Stria of Retzius;B, Enamel tuft;

C, Enamel lamella;

D, Dentino-enamel junction


24/151

Chapter 2, Slide 3Neonatal line

The neonatal line is a dark stria of Retzius that occurs at the time of birth. It is

due to the stress of birth. The neonatal line is usually the darkest and thickest

stria of Retzius. The enamel at the cusp of the tooth generally exhibits a wavypattern. This enamel is called gnarled enamel. This is NOT hypo-mineralized.

The enamel rods are laid down in this pattern by

ameloblasts to make the enamel strong in this region.

A, Gnarled enamel; B, Neonatal line;

C, Dentin; D, Dentino-enamel junction


25/151

Chapter 2, Slide 4Straight enamel rods - longitudinal

labiolingual section

The enamel rods project in the direction of the arrow.

Can you see the stria of Retzius?


26/151

Chapter 2, Slide 5Gnarled enamel

Enamel rods are general not

straight throughout their length.

In the cuspal region, the rods are

very wavy. This is referred to as

gnarled enamel. In this section,you can see the end of an

odontoblastic process

penetrating the enamel just past

the DEJ.

This structure is called an

enamel spindle.A, Gnarled enamel;

B, Enamel spindle


27/151

Chapter 2, Slide 6Cross-striations

Eachenamel rod demonstates closely positioned striations along itslength known as cross-striations or incremental lines. These are thought to be

formed by the daily rhythm of the ameloblast laying down more and less

mineralized enamel. The striations are approximately 5 m apart. This distance

represents one day of enamel deposition. In this micrograph rods project in the

direction of the arrow. Can you see the striations on each rod? They are oriented

perpendicular to the length of the rod.

Note: Not the large dark bands projecting diagonally; these are

stria of Retzius.


28/151

Chapter 2, Slide 7Enamel cut

In enamel cut in perfect cross-section the shape of the enamel

rod exhibits a "keyhole"-shaped pattern. However, in a normalcross-section of enamel, as seen here, most rods are cut obliquely.

This is because they do not travel in a straight line.

The micrograph on the left is produced by differential interference

microscopy while the micrograph on the right is from transmitted light

microscopy.


29/151

Chapter 2, Slide 12Hunter-Schreger bands

Hunter Schreger bands are

seen here with special

illumination in

longitudinal ground

sections of enamel as light

and dark bands.

The red arrows indicate

three light bands.


30/151

Chapter 2, Slide 13Enamel tufts

Enamel tufts are lessmineralized areas of enamel

in the inner third of enamel

adjacent to the DEJ. They

resemble tufts of grass. They

are wavy due to the

waviness of the adjacent

rods. Structures rich in

organic matter

(i.e. less mineralized) that

project to the surface of the

enamel areenamel lamellae.

A, Enamel tufts;

B, Enamel lamella


31/151

Chapter 2, Slide 14Enamel tufts - two planes of focus

Enamel tufts consist of

several unconnected

"leaves" of hypo-

calcified enamel.

They display a wavy twisted

appearance. Enamelspindles are the processes of

odontoblasts projecting into

the enamel.A, Enamel spindle;

B, Enamel tuft


32/151

Chapter 2, Slide 15

Enamel tuftsaligned in rows

Enamel tufts are aligned in

rows. They may represent

planes

Of tension during

developmentA, Enamel tufts;

B, DEJ;C, Dentin


33/151

Chapter 2, Slide 16Enamel lamellae

In this ground cross-section oftooth,

you can see enamel lamellae

and enamel

tufts You can also see

the neonatal line.

What do all three of

these structures have

in common?A, Enamel lamella;

B, Enamel tuft;C, Neonatal line

Answer:

They are all hypocalcified.


34/151

Chapter 2, Slide 17Decalcified tooth

In a decalcified section of

tooth, only the organic

material is left behind.

In this micrograph you can

see an enamel

lamella and enamel

tufts.

A, Enamel lamella;B, Enamel tuft


35/151

Chapter 2, Slide 18Odontoblast process

Odontoblast processes usuallyend at the DEJ. However,

sometimes

the ends of the process

become embedded in the

enamel as it forms.

These very small, usually

straight structures that you can

see adjacent to

the DEJ are enamel

spindles. They are only about

one tenth the lengthof an enamel tuft.

A, Enamel spindle;

B, Odontoblast

processes in dentin


36/151

Chapter 2, Slide 19Enamel spindles

In this high magnification

of the DEJ you can clearly

see the bifurcation of the

ends of some of theodontoblast processes as

well as enamel spindles.

A, Enamel spindle;B, Odontoblast process;

C, Enamel rod


37/151

Chapter 3DENTIN


38/151

Chapter 3, Slide 1Contour lines of Owen

During development of dentin,

variations in the metabolism ofthe organism cause variations in the

amount of organic material deposited

in the dentin, just as occurs in the

enamel. Changes in the coloration of

the dentin are called contour lines of

Owen. The first dentin that is laid

down (at the DEJ) forms the mantlelayer while subsequent dentin forms

the circumpulpal layer. In the crown of

tooth, dentinal tubules from

S-shaped primary curves.A, Contour line of Owen;B, Mantle layer of dentin;

C, Circumpulpal layer of

dentin;

D, DEJ


39/151

Chapter 3, Slide 2

Contour lines of Owen and Stria of

RetziusThe contour lines of Owen

intercept the dentino-enameljunction and meet an

accompanying Stria

of Retzius that was formed at

the same timeA, Contour line of Owen;

B, Stria of Retzius


40/151

Chapter 3, Slide 3Lines of vonEbner

Daily alterations in the

formation of dentin

produce imbrication lines

of von Ebnor that are

approximately 5 m in

length, are seen as

banding along thedentinal tubules and are

comparable to the

cross-striations in

Enamel. Arrow indicates

the direction of the linesof von Ebnor that are

perpendicular to the

dentinal tubules.


41/151

Chapter 3, Slide 4Dentinal tubules

Each odontoblast has a long

process that projects through thedentin to the DEJ. The hole or tube

in the dentin through which this

process projects is called the

dentinal tubule. The course of the

dentinal tubules in the crown of the

tooth is S-shaped due to thecrowding of the odontoblasts as

they get squeezed into a smaller

and smaller space within the pulp

cavity. This curve is called a

primary curve.

A, Primary curve

of dentinal tubule;

B, DEJ; C, Mantle dentin;

D, Circumpulpal dentin


42/151

Chapter 3, Slide 5

OdontoblastsOdontoblasts in an erupted tooth

As the dentin layer forms, the

odontoblast become increasingly

crowded as they are squeezed

into a smaller area. The single

layer of odontoblasts (as occurs

in early development) has now

changed to stacks of

odontoblasts.A, Odontoblasts;

B, Predentin;

C, Pulp cavity;

D, Dentinal tubules


43/151

Chapter 3, Slide 6Secondary curves

During the deposition of

dentin, the odontoblast makes

slight undulations that creates

wavy dentinal tubules. This

waviness

of the dentinal tubules is

called secondary curves.

A, Secondary curve of

dentinal tubule


44/151

Chapter 3, Slide 7Mantle dentin

When viewed in polarizedLight, mantle dentin (red

band), which is about

10 m wide, can be

differentiated from

circumpulpal dentin(purple with black dentinal

tubules).This

is due to a difference

In the collagen fibers

in mantle dentin.

A, Enamel;

B, Circumpulpal dentin;

C, Mantle dentin


45/151

Chapter 3, Slide 8Globular calcification

of dentinDentin is calcified after it

is formed. The calcification

begins in small spherical

areas. These become larger

and fuse with one another to

form a calcification front(row of calcification sheres

along the

predentin edge).A, Odontoblasts;

B, Predentin;

C, Calcification front;

D, Calcified dentin


46/151

Chapter 3, Slide 9Calcification pattern of

dentin - decalcified

SectionIn mature dentin, globules

of well-calcified dentin areapparent (arrow) along

with Areas of less calcified

dentin

(white areas).

A, Globule of

well-calcified

dentin


47/151

Chapter 3, Slide 10Interglobular dentin in

globular layer - ground sectionBetween the mantle and

circumpulpal layers is a layer of

dentin in which the calcified

globules do not fuse evenly.

This is called the globular layer.

In a ground section of dentin,the less-calcified areas of dentin

appear as irregularly

shaped crescents called

interglobular dentin.

A, Interglobular dentin

Ch t 3 Slid 11


48/151

Chapter 3, Slide 11Globular layer and granular layer

In the root of the tooth,

the peripheral border of mantle

dentin adjacent to the cementumhas a granular appearance and is

called the granular layer of Tomes.

The granular layer is a less calcified

layer like that of the globular layer.

Generally, interglobular dentin is

seen only in the crown, but in this

specimen it extends into the root.A, Circumpulpal layer;

B, Globular layer;

C, Mantle layer;D, Granular layer;

E, Cemento-enamel junction;

F, Enamel;

G, Cementum


49/151

Chapter 3, Slide 12Dentinal tubules

Dentinal tubules are the hollowtubes that run through the dentin in

which are located the odontoblastic

processes. During formation of

dentin, intertubular dentin is laied

down between the odontoblastic

processes. Then a second layer of

more mineralized dentin is added to"coat" the inside of the tubules. This

layer of dentin is called peritubular

dentin or intratubular dentin. In this

scanning electron micrograph, the

peritubular dentin

appears white.A, Peritubular dentin;

B, Intertubular dentin;

C, Dentinal tubule


50/151

Chapter 3, Slide 13Dentinal tubular branches in root -

transmitted and differential

interface contrast microscopy

Dentinal tubules generallyhave lateral branches where

odontoblastic processes can

communicate with one

another. These branches, asseen here, are most

numerous in the root of the

tooth.

A, Odontoblastic process;

B, Lateral branches of

dentinal tubules

Chapter 3, Slide 14


51/151

pTerminal branching of dentinal

tubules

Dentinal tubules are closely

spaced but have a large diameterclose to the pulp cavity. Dentinal

tubules become more widely

spaced in the dentin but have a

narrower diameter as they

approach the DEJ. At the DEJ,

dentinal tubules branch. Thiscauses an increased dentity of

dentinal tubules in cross-sections

of dentin in this region. In this

micrograph, note the scalloped

appearance of the DEJ. The peaks

of the scallops point toward theenamel.

A, Dentinal tubule;

B, DEJ; C, Enamel;

D, Enamel spindle

Ch t 3 Slid 16


52/151

Chapter 3, Slide 16Forms of dentin

Primary dentin, with straight tubules, is

laid down before completion of the

apical foramen. Regular secondarydentin is characterized by a slower rate

of deposition and an abrupt change in

the direction of the dentinal tubules.

Tertiary or irregular secondary (also

called irritation, reparative or reactive)

dentin is laid down in response to an

irritation or damage to the overlying

dentin and/or enamel .This dentin has

irregularly arranged and few dentinal

tubules. With aging or severe damage,

tertiary dentin can totally obliterate the

pulp cavity.

A, Primary dentin;

B, Secondary (regular) dentin;

C, Reactive dentin

Ch t 3 Slid 17


53/151

Chapter 3, Slide 17Dead tracts and blind tracts

When dentin is damaged,

odontoblastic processes die or retract

leaving empty dentinal tubules. Areas withempty dentinal tubules are called dead

tracts and appear as dark areas in ground

sections of tooth. With time, these dead

tracts can become completely filled in

mineral.

This region is called blind tracts and

appears white in sections of ground tooth

.The dentin in blind tracts is called sclerotic

dentin. The adaptive advantage of blind

tracts is the sealing off of the dentinal

tubules to prevent bacteria from entering

the pulp cavity.

A, Dead tract;

B, Blind tract

(containing sclerotic dentin)


54/151

Chapter 4THE PULP


55/151

Chapter 4, Slide 1

PulpThe pulp cavity occupies the

central area of the tooth

enclosed by dentin. The pulp

has the cellular, fibrous, neural

and vascular components of

typical loose connective tissue.

The main function ofthe pulp is the production

and maintenance

of the dentin.A, Pulp cavity;

B, Dentin;

C, Odontoblasts


56/151

Chapter 4, Slide 2

Nerve Plexus of RaschkowSensory nerve fibers that originate from inferior and superior alveolar nerves

innervate the odontoblastic layer of the pulp cavity. These nerves enter the tooth through the

apical foramen as myelinated nerve bundles. They branch to form the subodontoblastic nerve

plexus of Raschkow which is separated from the Odontoblasts by a cell-free zone of Weil. In

addition to the sensory nerves, sympathetic

nerve bundles also enter the tooth to innervate blood vessels.A, Odontoblasts; B, Cell-free zone of Weil; C, Nerve plexus of Raschkow


57/151

Chapter 4, Slide 3

Vascular supply of pulp cavity

The pulp cavity receives

blood from one arterial that

enters the apical foramen and

courses directly to the coronal pulp.

Within the coronal pulp numerousarterial branches form a interconnected

network of blood vessels as seen here

following

filling with ink. The smallest capillary

loops are in the subodontoblastic

zone (arrow).


58/151

Chapter 4, Slide 4Structures within the pulp cavity

Arterioles, small nerve bundles and

fibroblasts are found in the pulp cavity.A, Nerve bundle;

B, Arteriole; C, Fibroblasts


59/151

Chapter 4, Slide 5Structures within the pulp cavity

Arterioles can be distinguished from

venules within the pulp cavity by thethickness and contours of their vascular

walls.

A, Arteriole;

B, Venule;

C, Nerve bundle (cut in cross-section)


60/151

Chapter 4, Slide 6

Subodontoblastic region

Below the odontoblastic layer

is the cell-free zone of Weil

followed by a cell-rich zone which is

thought to provide replacement cells

for odontoblasts that die.

Within these zones are

the nerve plexus of Raschkow and

capillary network.

A, Cell-rich zone;

B, Cell-free zone;C, Odontoblastic layer;

D, Dentin


61/151

Chapter 4, Slide 7

Denticle

The formation of a true pulp stone or

denticle is brought about by the

differentiation of pulp cells to

odontoblasts within the pulp cavity.

The resulting body has anappearance characteristics of dentin

with tubules radiating out from the

center and predentin around

the periphery.

A, True pulp stone;B, Pulp cavity;

C, Dentin


62/151

Chapter 4, Slide 8

False pulp stoneThe formation of a false

pulp stone is caused by the

nonspecific calcification of tissue

around a central nucleus within

the pulp cavity. This pulp stone ischaracterized by concentric

layers of mineralization rather

than radiating tubules as seen in

true pulp stones.A, False pulp stone;

B, Pulp cavity


63/151

Chapter 4, Slide 9

Regions of the pulp cavityThe pulp cavity can be

divided into two main

regions: the coronal pulp is

located within the crown ofthe tooth and the radicular

pulp is located within the

root.

A, Coronal pulp;

B, Radicular pulp


64/151

Chapter 5

cementum


65/151

Chapter 5, Slide 1

Acellular versus cellular cementumDuring the formation of the root,

acellular cementum is layed

down mainly in the pericervical

(upper) region of the root.

Cellular cementum is laid down

after eruption and throughout

life, and is located in the

periapical (lower) and

interradicular regions

of the root.A, Acellular cementum;B, Cellular cementum


66/151

Chapter 5, Slide 2Fused root tips

The continued deposition of

cementum is illustrated in this

cross-section of molar roots.

The interradicular cementumof the roots is fused together

(arrow).A, Cellular cementum;

B, Dentin;C, Interradicular

cementum


67/151

Chapter 5, Slide 3

Cementocytes

Cementoblasts lay down cementum on the surface of root dentin.

Some cementoblasts become embedded in the cellular cementum.These cells are called cementocytes. Cementocytes are housed in hollow

spaces in the cementum called lacunae. The processes of the cementocytes project

toward the periodontal ligament in small tubes in the cementum

called canaliculiA, Cementocyte in lacuna; B, Process of cementocyte in canaliculi

Chapter 5, Slide 4


68/151

Sharpey's fibers in acellular cementumThe periodontal ligament is made of

large collagen fibers that course between the

cementum and the alveolar Bone. These fibers

are embedded in the outer layer of cementumand are called Sharpey's fibers. They project into

the cementum between groups ofcementoblasts,

and lie perpendicular to the surface of the

cementum (direction indicated by the blue

arrow). The cementoblasts also lay down fine

collagen fibers in the cementum which lie parallel

to the surface of the cementum (directionindicated by the green arrow).

In this micrograph of acelluar cementum

(bracket) the dentino-cementum junction

can be seenA, Periodontal ligament fibers;

B, Sharpey's fibers;C, Dentino-cementum junction;

D,Cementoblasts;

E, Acellular cementum


69/151

Chapter 5, Slide 5Arrest or resting linesCementum is layed down at

intervals as evidenced by the

appearance of arrest lines

(light and dark bandingpattern) in the cementum.

These lines indicate

alternating periods of

deposition and lack of

deposition of cementum.

A, Arrest lines;

B, Dentin


70/151

Chapter 5, Slide 6

Cementum lamellaeIn polarized light, a banding

pattern in cementum is seen

indicating alternating directionality

of collagen fibers in cementum

running parallel to the root surface.

Collagen fibers of the periodontal

ligament run perpendicular to the

root surface.A, Cementum;

B, Granular layer of dentin;

C, Periodontal ligament


71/151

Chapter 5, Slide 7

CementiclesCalcified bodies are

sometimes found in the

periodontal ligament. These

are called cementicles and

are formed in a number of

ways. Some are formed from

the calcification of epithelial

rests.A, Periodontal ligament;B, Cementicle


72/151

Chapter 5, Slide 8

Attached cementicleCementicles may be free in the

periodontal ligament, attached

to the surface of cementum or

embedded in the cementum. In

this micrograph a cementicle isembedded in the cementum

layer.A, Embedded cementicle;

B, Periodontal ligament;

C, Alveolar bone


73/151

Chapter 6

Periodontal

ligaments


74/151

Chapter 6, Slide 1

Alveolar boneThe tooth is anchored to the surrounding alveolar bone by the periodontal ligament. The

alveolar bone directly surrounding the tooth cavity is called cribriform plate. The layer of

cribriform plate into which the collagen fibers of the ligament are anchored is called bundle

bone. The bone underlying the gingiva is called cortical plate (not shown). Cribriform and

cortical plates are both compact bone, and are separated by spongy bone in the center ofalveolar bone. The bone inferior to alveolar bone (jaw bone) is called basal bone (not

shown) and is very thick.A, Cem,entum; B, Periodontal ligament; C, Cribiform plate; D, Marrow

cavity of spongy bone; E, Bundle bone; F, spongy bone.


75/151

Chapter 6, Slide 2

Interdental septumThe bone between teeth is

called the interdental septumand is composed entirely of

cribriform plateA, Interdental septum;

B, Periodontal ligament

Chapter 6, Slide 3


76/151

pPeriodontal ligament

The periodontal ligament is anchored

in cementum of the tooth and the bundlebone layer of the cribriform plate. Interstitial

spaces contain blood vessels and nerves

between collagen bundles of the

periodontal ligament. Both cementum and

cribriform plate can show arrest lines

indicating alterations in the deposition ofcementum and bone by cementoblasts and

osteoblasts, respectively.

Alveolar bone is compact

bone and shows osteons.A, Dentin; B, Cementum;

C, Periodontal ligament; D, Osteon;

E, Interstitial space;

F, Arrest lines in cribiform plate;

G, Cribiform plate.


77/151

Chapter 6, Slide 4

Nonfunctional periodontiumIn the absence of function of

the tooth, the periodontal

ligament becomes narrow

and looses the organizationof the fiber bundles.A, Periodontal ligament;

B, Cementum;

C, Cribriform plate

C 6 S i


78/151

Chapter 6, Slide 5

Gingival and alveolar crest fibersThe most cervical region of

alveolar bone is the alveolar

crest.

Alveolar crest fibers (the

cervical most fibers of the

periodontal ligament) attach to

the alveolar crest. Gingival

fibers extend from the cervical

cementum of the tooth into the

gingiva.A, Gingival fibers;

B, Alveolar crest fibers;

C, Alveolar crest


79/151

Chapter 6, Slide 6

Horizontal fibersApical to the alveolar crest

fiber group is the horizontal

fiber group of theperiodontal ligament

A, Horizontal fiber group;

B, Alveolar crest fiber

group;

C, Gingival fibers;

D, Alveolar crest


80/151

Chapter 6, Slide 7

Oblique fiber groupApical to the horizontal

fiber group is the oblique

fiber group of the

periodontal ligament.A, Oblique fiber

group,,


81/151

Chapter 6, Slide 8

Periapical fiber groupIn the region of the apex of

the root is the periapical fiber

group of the periodontal

ligament.

The neurovascular bundlecourses between these fibers

to enter the apical foramen.A, Periapical fiber group;

B, Neurovascular bundle;C, Apical foramen


82/151

Chapter 6, Slide 9

Interradicular fiber groupIn multi-rooted teeth, the

interradicular fiber group of

the periodontal ligament is

located close to the crown

between the roots. Theseattach to interradicular bone

(septum).A, Interradicular fiber

group;

B, Interradicular bone


83/151

Chapter 6, Slide 10

Transseptal fibersTransseptal fibers extend

from the cementum of one

tooth, over the interdental

bone (septum) to the

cementum of the adjacenttooth.

These fibers keep

all the teeth alignedA, Transseptal fibers;

B, Interdental bone


84/151

Chapter 6, Slide 11

Interstitial spaces

Interstitial spaces are regions

of loose connective tissue

located between periodontal

fiber bundles. These regions

contain fibroblasts, blood

vessels, and nerves and are

responsible for providing

nutrients to the periodontal

ligament and cells of the

cementum.A, Interstitial fibers


85/151

Chapter 6, Slide 12

Cells of the periodontal

ligamentThe main type of cell in the

periodontal ligament is the

fibroblasts. Adjacent to the

cementum are

cementoblasts, and

adjacent to the cribriform

bone are osteoblasts.A, Fibroblasts;

B, Cementoblasts;C, Osteoblasts


86/151

Chapter 6, Slide 13

Epithelial rests

(of Malassez)Remnants of the epithelial

root sheath that remain

following its disintegration

during root formation are

called epithelial rests.These are located in the

periodontal ligament.A, Epithelial rests;

B, Cementum;

C, Periodontal ligament


87/151

Chapter 6, Slide 14Intermediate zone in transmitted and polarized light

In the developing periodontal ligament during eruption of the tooth, three zones can be recognized:

zone adjacent to cementum, zone adjacent to bone and an intermediate zone. This zonerepresents a transition zone between the original structure of the dental sac and the adult structure

of the periodontal ligament. In polarized light it is apparent that the collagen fibers run in a direction

opposite to those in the other two zones.A, Predentin; B, Circumpulpal dentin; C, Mantle dentin;

D, Periodontial ligament; E, Intermediate zone


88/151

Chapter 6, Slide 15

Bone resorptionTooth movement (by normal mesial drift or orthodontics) can cause cementum and

bone resorption. Tooth movement toward the cribriform plate stimulatedosteoclasts to resorb bone to make room for the new position of the tooth. The

scalloped-shaped resorbed are is

called a resorption lacuna.A, Direction of tooth movement;

B, Resorption lacuna; C, Osteoclast


89/151

Chapter 6, Slide 16

Bone deposition

Tooth movement (by normal mesial drift or orthodontics) can cause bone deposition.

Tooth movement away from the cribriform plate stimulates osteoblasts to lay down

new bone, thus filling in the space left by the repositioning of the tooth. New bone iswoven bone and extends from an arrest line. Periodontal fibers are anchored in this

new bundle boneA, Direction of tooth movement;

B, Woven bone (new bone deposition);

C, Arrest line


90/151

Chapter 6, Slide 17

Woven and lamellar boneNew woven bundle bone has a different appearance than the lamellar

bone which it has replaced in this ground sectionof tooth and bone.

A, Osteon of lamellar bone;

B, Woven bundle bone; C, Periodontal ligament;

D, Cementum


91/151

Chapter 6, Slide 18Gingival epithelium

The gingival epithelium facingthe tooth is divided into the

sulcular (unattached) and

junctional (attached) epithelia

and is nonkeratinized.

The gingival epithelium facing

the oral cavity is keratinized and

displays numerous rete pegs

(extensions of stratified

squamous epithelium into the

underlying lamina propria).A, Sulcular epithelium;

B, Junctional epithelium;

C, Rete pegs


92/151

Chapter 7

TEETHERUPTION


93/151

Chapter 7, Slide 1

Pre-eruptive stageThe pre-eruptive stage of tooth development is that time before the initial

formation of the root. During root development the tooth begins to erupt. This

micrograph shows the beginning of the appositional stage when dentin and

enamel begin to be deposited.A, Enamel organ; B, Dental lamina; C, Basal bone

Chapter 7 Slide 2


94/151

Chapter 7, Slide 2

Pre-functional eruptive stageDuring the pre-functional eruptive

stage the root forms and the tooth

erupts until it reaches functional

occlusion (it meets the opposing

tooth). In this micrograph a lateral

deciduous incisor is beginning to

form a root and erupt. The enamelorgan of the permanent incisor is

seen lingually to the erupting

tooth.A, Erupting incisor during pre-

functional eruptive stage;B, Permanent incisor;

C, Basal bone.


95/151

Chapter 7, Slide 3

Fusion of reduced enamel epitheliumand oral mucosa

Just prior to the tooth breaking

through the oral mucosa, the

reduced enamel epithelium fuses

with the oral mucosa. Themucosa at the site of eruption will

form the gingival epithelium.A, Erupting incisor;

B, Permanent incisor;

C, Reduced enamel

epithelium


96/151

Chapter 7, Slide 4

Clinical eruption

The penetration of the tooth

through the reduced enamel

epithelium and oral mucosa

represents clinical eruption.

During this time a bony partitionforms between the erupting

deciduous tooth and permanent

developing tooth.A, Erupted deciduous tooth;

B, Permanent tooth;C, Bony partition


97/151

Chapter 7, Slide 5

Functional eruptive stageFollowing the complete

eruption of a tooth, the

tooth further erupts small

distances during its life

time due to the wearingdown of the incisal edge or

cusp.A, Erupted deciduous

tooth;

B, Permanent tooth


98/151

Chapter 7, Slide 6

Root resorptionDuring the growth and

eruption of the permanent

tooth, the root of the

deciduous tooth is resorbed.

This resorption occurs dueto the pressure placed on

the root by the erupting

permanent tooth. A. Area of

root resorptionA, Area of root resorption


99/151

Chapter 7, Slide 7

OsteoclastsOsteoclast-like cells are

stimulated by the pressure

from erupting permanent

teeth and resorb the root.

These cells line up alongthe root and form

resorption lacuna

(scalloped shaped areas

of root resorption).A, Osteoclast-like cells

Ch t 7 Slid 8


100/151

Chapter 7, Slide 8Intermittent resorption

During root resorption,periods of resorption are

alternated by periods of

cementum repair.

Cementoblasts deposit

cementum in areas of

resorption forming a reversalline. Some cementoblasts

become embedded in the

cementum and are then

called cementocytes.A, Reversal line;

B, Cementoblasts;

C, Cementocyte


101/151

Chapter 7, Slide 9

Shed incisor (dentin)Shedding of teeth usually entails

complete destruction of the root.

Resorption lacuna can be seen in

cervical region of the shed tooth.

In this micrograph note thereparative dentin below the worn

incisal edge.A, Resorption lacunae;

B, Incisal edge of shed tooth;C, Reparative dentin


102/151

Chapter 7, Slide 10

Eruption of the permanent incisor

During eruption of the permanent

tooth its position may shift

buccally (especially after the

deciduous tooth has been shed).

The apical foramen does not

reach its final diameter untilfunctional occlusion

A, Erupting of the permanent

incisor;

B, Apical foramen


103/151

Chapter 7, Slide 11

Functional active eruptionAfter the permanent tooth

has reached its final occusal

position, it may further erupt

due to incisal wear. Inaddition, passive eruption

can take place which involves

recession of the gingiva.A, Mature tooth;

B, Gingiva


104/151

Chapter 7, Slide 12Reduced enamel epithelium

At the conclusion of enamel formation the enamel organ is reduced to a fewlayers of cuboidal cells called the reduced enamel epithelium. This layer forms

the junctional epithelium facing the tooth following eruption.A, Reduced enamel epithelium


105/151

Chapter 7, Slide 13

Reduced enamel epithelium

During eruption much mitotic

activity occurs in the basal layers

of the reduced enamel epithelium

and oral mucosa. Upon tooth

penetration into the oral cavity

these two layers fuse and provide

cells for the epithelium facing the

tooth.A, Reduced enamel

epithelium; B, Enamel space;C, Dentin;

D, Oral mucosa


106/151

Chapter 7, Slide 14

Transformation of reduced

enamel epitheliumDuring eruption the reduced

enamel epithelium is

transformed into stratified

squamous epithelium.A, Stratified squamous

epithelium adjacent to

cervix of tooth.


107/151

Chapter 8

THE ORAL

CAVITY

Chapter 8, Slide 1


108/151

p

LipThe oral mucosa (lining of the oral

cavity) consists of stratified

squamous epithelium. Here on

the inside of the lip the epithelium

is nonkeratinized; it lacks a

keratin layer. Underlying the

epithelium is the lamina propria

which consists of

loose connective tissue.

Minor seromucous salivary

glands are also present.A, Stratified squamous

epithelium, nonkeratinized;

B, Lamina propria;

C, Seromucous salivary gland


109/151

Chapter 8, Slide 2

Squamous epithelial cell (transmitted and phase contrast)

Nonkeratinized squamous epithelial cells of the inside of the cheek

demonstrate a flat appearance, a prominent nucleus, and ridges (dark lines,

arrow) caused by the close packing of neighboring cells.


110/151

Chapter 8, Slide 3

Transition between gingiva and alveolar mucosaGenerally the oral epithelium is keratinized where there is the most abrasion and where

the mucosa is directly connected to bone. In this micrograph, you can see the difference

in appearance of the nonkeratinized stratified squamous epithelium of the alveolar

mucosa and the keratinized stratified squamous epithelium of the gingiva.

The keratinized epithelium has long rete pegs and corresponding connective tissuepapilla. These two features help secure the epithelium to the underlying connective

tissue and maintain its integrity during the application of abrasive forces (chewing).A, Keratinized stratified squamous epithelium (gingiva);

B, Nonkeratinized stratified squamous epithelium (alveolar mucosa);

C, Lamina propria; D, Rete peg; E. Connective tissue papilla

Chapter 8, Slide 4

Lip histology


111/151

p gyThe lip provides an example of thin

keratinized stratified squamous

epithelium of the outside skin, and thicknonkeratinized stratified squamous

epithelium of the inside oral mucosa.

The transitional zone between these

two regions is the red margin which

consists of keratinized epithelium. Minor

mucoserous salivary glands are locatedunder the oral mucosa.A, Keratinized stratified

squamous epithelium (skin);

B, Red margin;

C, Nonkeratinized stratifiedsquamous epithelium

(oral mucosa);

D, Minor mucoserous

salivary glands


112/151

Chapter 8, Slide 5

Skin of the lipThe skin of the lip consists of keratinized stratified squamous epithelium inwhich hair follicles, sweat glands and sebaceous glands can be seen. Sweat

glands are tubular glands that empty onto the surface of the skin, while

sebaceous glands empty into hair follicles.A, Sweat gland; B, Sebaceous gland; C, Hair follicle


113/151

Chapter 8, Slide 6Red margin

The red margin is very thin keratinized epithelium with no hair follicles or sweat

glands. The orbicularis oris muscle fibers come closeto the red margin.A, Red margin;

B, Nonkeratinized oral mucosa;

C, Orbicularis oris muscle


114/151

Chapter 8, Slide 7Cheek epithelium

Nonkeratinized stratified squamous epithelium consists of layers of living cells. The

cells of the upper layers of epithelium appear clear due to fluid in the cells. The fluid

protects the underlying layers against machanical damage. The epithelium is divided

into layers: the deepest layer, stratum basale provides progenitor cells to renew theepithelium, the stratum spinosum consists of variable-shaped cells connected

together by desmosomes. The cells in the upper most levels of

the spinosum layer are flat.

A, Stratum basale; B, Stratum spinosum; C, Oral cavity


115/151

Chapter 8, Slide 8

Submucosa of the lipThe submucosa of the oral cavity is composed of dense connective tissue

containing blood vessels, nerves and mixedseromucous glands.

A, Mixed seromucous glands;

B, Dense connective tissue;

C, Blood vessels


116/151

Chapter 8, Slide 9

Gingival epitheliumAttached gingiva is located apical to the gingival sulcus. It is generally parakeratinized

stratified squamous epithelium which means that the upper layer of cells is dead but retain

their nuclei. Characteristics of keratinized epithelium is the presence of very long rete pegsand connective tissue papillae. The attached

gingiva lacks a submucosa and is directly attached to bone.A, Rete peg; B, Connective tissue papilla;

C, Oral cavity adjacent to attached gingiva;

D, Parakeratinized stratified squamous epithelium.


117/151

Chapter 8, Slide 10

Stippling of gingivaIn healthy gingival epithelium

"stippling" is often seen which

appear as small pits in the

epithelium. These are due to the

deep rete pegs. In this micrograph

of attached epithelium, you can seea layer of keratin. The upper layer

of cells have lost their nuclei and

the epithelium is called

orthokeratinized.A, Stippling of gingiva;

B, Keratin layer


118/151

Chapter 8, Slide 11Adipose tissue of hard palate

The lamina propria of the mucosa of the hard palate in the midline region

(median raphe) serves at the periosteum of the bone and thus the mucosa iscalled a mucoperi-osteum. A submucosa with adipose tissue exists in the

anterolateral region of the hard palate. The epithelium

of the hard palate is keratinized.A, Adipose tissue; B, Oral cavity; C, Mucoperiosteum;

D, Dentin of tooth; E, Alveolar bone


119/151

Chapter 8, Slide 12

Glandular zone of the hard palateIn the posterolateral region of the hard palate the submucosa

contains seromucous glands.A, Seromucous glands;

B, Mucoperiosteum


120/151

Chapter 8, Slide 13

Posterior hard palate

The seromucous glands extend into the midline of the posterior region of thehard palate which is adjacent to the soft palate.

A, Seromucous glands


121/151

Chapter 8, Slide 14Sagittal view of hard and soft palates

The epithelium of the soft palate is nonkeratinized. It overlies

a lamina propria, submucosa and muscle. Dorsal to the hardandsoft palate is the nasal cavity.A, Hard palate;

B, Soft palate;

C, Nasal cavity


122/151

Chapter 8, Slide 15

Incisive papilla

Just posterior to the central

incisors, there is an elevation of the

oral mucosa called the incisive

papilla. Sometimes, a nasopalatine

duct (lined with pseudo-stratified

ciliated epithelium) is present thatopens via the incisive foramen into

the incisive papilla.A, Nasopalatine duct;

B, Keratinized stratified

squamous epithelium


123/151

Chapter 8, Slide 16Filiform papilla

The surface of the tongue is

covered with epithelial protrusions

called papilla.

The most numerous of thesepapillae is the keratinized filiform

papilla which is non-sensory and

gives the

tongue a rough

surface.

A, Filiform papilla


124/151

Chapter 8, Slide 17

Scanning electron micrograph of

filiform papillaFiliform papillae resemble spiky

hairs or bristles and allow thetongue to be used for lapping up

liquids and moving substances

around

in the mouth.A, Filiform papilla


125/151

Chapter 8, Slide 18

Fungiform papillaMushroom-shaped papilla called fungiform papilla possess taste buds (onion-

shaped groupings of sensory cells) on their dorsal surface. The epithelium

overlying the sensory papillae is generally nonkeratinized or very lightlykeratinized. The fungiform papilla are dispersed over the anterior region of the

dorsal tongue; perceive sweet, salty and sour; and are innervated by the

seventh cranial nerve.A, Fungiform papilla

Chapter 8, Slide 19

Circumvallate papilla


126/151

A V-shaped row of about eight very

large papilla called circumvallate

papilla exist on the posterior tongue.

These papilla are surrounded by a

deep trough (groove in the mucosa).

Taste buds are located down within the

groove, and detect bitter substances.

Special serous glands called von Ebnerglands secrete into the base of the

troughs to wash out the bitter

substances after taste bud stimulation.A, Circumvallate papilla;

B, von Ebner gland;C, Trough;

D, Taste bud


127/151

Chapter 8, Slide 20

Taste bud

Chemical substance in the oral cavity stimulate taste bud sensory cells through a

small opening in the epithelium called the taste pore. The taste bud contains

sensory cells (with apical microvilli), supporting cells and basal cells, the latterproviding new cells for the taste bud every 5 to 10 days. Upon stimulation,

sensory cells release chemicals from their basal membrane to stimulate sensory

nerve endings from taste ganglion

cells which relay the input to the brainstem.

A, Taste bud; B, Taste pore; C, Basal cell; D, Sensory cell


128/151

Chapter 8, Slide 21Scanning electron micrograph

of taste poreThe taste pore is an opening in the

layer of epithelial cells covering the

surface of the taste bud. Tastesubstances enter the taste pore and

stimulate the apical microvilli

of taste bud sensory cells.A, Taste pore;

B, Taste bud


129/151

Chapter 8, Slide 22Vascular supply of the tongue

he epithelium of the oral cavity is nourished by an extensive capillary plexus

which projects into the connective tissue papilla between the rete pegs. This

micrograph of tongue following a vascular dye injection illustrates the rich

vascular supply of the tongue especially within the connective tissue papillaeA, Capillary network within connective tissue papilla


130/151

Chapter 9

THE SALIVARYGLANDS


131/151

Chapter 9, Slide 1

Fetal submandibular salivary glandThe organization of salivary glands is best understood by observing

a developing salivary gland. Salivary glands are divided into lobes and lobules containing

secretory acini and ducts. Lobes and lobules are separated by

connective tissue partitions. Acini are composed of either serous or mucous cells. They empty

into intercalated, striated and excretory ducts, respectively.

Intercalated and striated ducts are located within lobules and excretory

ducts are located within connective tissue septa.

A, Salivary gland lobule; B, Excretory duct; C, Striated duct;

D, Acinus; E, Connective tissue partition or septum


132/151

Chapter 9, Slide 2

Parotid glandThe parotid gland, located subdermally just in front of the ear,

is composed of serous acini only. The intercalated ducts aresmaller than the acini and the striated ducts are larger.

A, Serous acini;

B, Striated ducts;

C, Ecretory duct


133/151

Chapter 9, Slide 3

Parotid gland ductsIntercalated ducts arise directly from the acini, consist of a simple cuboidal epithelium, and

are continuous with striated ducts. Intercalated ducts add bicarbonate to the saliva. Striated

ducts consist of a simple columnar epithelium. These ducts take sodium out of the saliva

making it more hypotonic. Striated ducts are named so because there basal membrane ishighly infolded giving the base of the cell a striated appearance. Striated ducts empty into

excretory ducts which do not modify the composition of the saliva. They consist of simple

columnar

to stratified cuboidal epithelium.

A, Intercalated duct; B, Striated duct; C, Excretory duct


134/151

Chapter 9, Slide 4

Acini and ductsDuct cells generally stain more palely than serous acini. Serous acini are

composed of cells with a round basally located nucleus and basophilicstaining secretory granules containing zymogen

granules. Serous cells secrete a enzyme-rich watery fluid.A, Serous acinus;

B, Striated duct


135/151

Chapter 9, Slide 5Myoepithelial cells

Transmission electron micrograph of a

myoepithelial cell. Myoepithelial cells

are spider-shaped cells that are

located on the surface of acini

between the acinar cells and theirbasement membrane. These cells

have contractile ability and are thought

to squeeze the saliva from the acini

and proximal ducts.A, Myoepithelial cell


136/151

Chapter 9, Slide 6

Submandibular glandThe submandibular gland is a mixed, but mostly serous gland. Mucous

acini appear as very light due to the removal of

mucigen granules during tissue processing.A, Mucous acini;

B, Serous acini


137/151

Chapter 9, Slide 7

Mucous and serous acini of submandibular glandMucous acini possess a larger lumen than serous acini. Mucous cells are

pyramidal in shape with a flattened nucleus pressed against the basalmembrane. The distal most portion of the mucous acinus is covered by a few

serous cells in the form of a half-moon

called a serous demilune.

A, Serous acinus; B, Mucous acinus;

C, Serous demilune


138/151

Chapter 9, Slide 8

Sublingual glandThe sublingual gland contains mostly mucous acini. Very few striated ducts arepresent in this gland and intercalated ducts

are almost absent.A, Mucous acini of sublingual gland


139/151

Chapter 9, Slide 9

Acini of sublingual glandEach mucous acinus is capped with a serous demilune.

A, Mucous acinus;

B, Serous demilunes


140/151

Chapter 9, Slide 10

Fetal palatine tonsilTonsils are protective structures located between the oral cavity and pharynx.

Tonsils consist of lymphoid tissue usually located deep to epithelial crypts. The

epithelium is sometimes difficult to distinguish because of the infiltration oflymphocytes. The tonsils are thought to be

a line of defense against infection. The palatine tonsil is located

on the posterolateral wall of the oral cavity.

A, Crypt;

B, Lymphatic tissue


141/151

Chapter 9, Slide 11

Palatine tonsilThe lymphatic tissue of tonsils consists of rows oflymphatic nodules.

A, Crypt;

B, Lymphatic tissue


142/151

Chapter 9, Slide 12

Lymphatic nodules of tonsilsThe lymphatic nodules display a lightly stained germinal center (where new

lymphocytes are generated) and a darker outer ring of densely packed

lymphocytes. These cellular components are supported

within a network of reticular fibers.A, Germinal center of tonsilar lymph nodule


143/151

Chapter 10

temperomandibular joint


144/151

Chapter 10, Slide 1

Coronal view of fetal TMJThe temperomandibular joint

consists of the head of the condyle,

articular disk and capsule, upper

and lower synovial cavities and

articular fossa. In this micrographthe condylar head is still growing

by endochondral ossification.A, Condylar head;

B, Articular disk


145/151

Chapter 10, Slide 2Sagittal section of TMJ

The anterior end of the

articular disk and capsule

are attached to the lateral

pterygoid muscle.A, Condylar head;

B, Articular disk;

C, Lateral pterygoid

muscle

Chapter 10, Slide 3

Endochondral growth of condylar

h d


146/151

headThe condylar head grows byendochondral ossification as

occurs at the epiphyseal plate of

long bones. The surface of the

condylar head consists of fibrous

layer, followed by a highly cellular

reserve zone, a proliferative zone,hypertrophic zone, calcifying zone

and bone.A, Fibrous layer;

B, Reserve zone;

C, Proliverative zone;

D, Hypertrophic zone;

E, Calcifying zone;

F, Bone


147/151

Chapter 10, Slide 4

Adult TMJ

The temporomandibular joint ginglymoarthrodial joint (meaning that it glides and rotates)

between the tubercles and fossa of the temporal bone and the head of the mandibular

condyle. An articular disk is separates an upper and lower synovial cavity and the entire

joint is surrounded by a articular capsule.

A, Condylar head; B, Tubercle of temporal bone;

C, Articular fossa;D, Articular disk; E, Upper synovial cavity;

F, Lower synovial cavity; G, Lateral pterygoid muscle;

H, Upper portion of posterior disk and capsule;

I Lower portion of posterior disk and capsule


148/151

Chapter 10, Slide 5

Articular tubercleThe adult articular tubercle is covered with a layer of thick dense fibrous

connective tissue. Here you can see that the tubercle is

composed of lamellar bone.A, Fibrous connective tissue layer;

B, Lamellar bone of tubercle


149/151

Chapter 10, Slide 6

Articular fossaThe morphology of the articular fossa (no thick fibrous tissue) indicates

that it does not play a role in the active function of the joint. In thismicrograph remodelling of the bone is apparent by

the presence of arrest lines in the bone.A, Arrest lines;

B, Fossa


150/151

Chapter 10, Slide 7

Articular surface of condylar headThe condylar head is covered with thick fibrous connective tissue, which with

age may turn to fibrocartilage.A, Fibrous connective tissue layer;

B, Lower synovial cavity

Chapter 10, Slide 8

A ti l di k


151/151

Articular diskThe articular disk is composed

of thick fibrous connective tissue.

In the thin center the fibers run

parallel to the surface but around

the peripheral portions of the

diskthe deep fibers are woven. The

thin center receives the mostabrasive forces and is

avascular while the edges

of the disk receive a rich

capillary network.A, Articular disk;

B Upper synovial cavity

Documents

Atlas of Oral Histology by Akramjuaim